I just found this halloween event, promoted by riot.
The instructions are really simple:
Share the link provided below with your friends or other players.
You will receive 1 point for each person you invite. 8 Points to get a code for 3500 rp.
Turn in your points and get free RP!
Visit the event: badwebsitedontvisitit
This is a clone website of the official league of legends site, i recommend everyone to not login or give any information on this website. Infact jsut to be safe dont even click on it.